Water plays an absolutely key role in establishing a new lawn. When turf is harvested most of the roots are left behind in the field. The rest of the roots are there in the roll, but are in fact no use for the absorption of water. New Roots are sent out from the base of the plants and quickly penetrate the soil. The length of time this takes will depend on the time of year, ten to fourteen days in spring/summer and up to four weeks in the autumn. A newly-laid lawn needs moisture immediately to encourage new root growth and to prevent dehydration.
When watering-in the turf for the first time, it is important to water as soon as soon as possible, especially on a hot day. Fresh turf will quickly dry out on a sunny and/or windy day. The only time we recommend watering turf in direct sunshine is at this initial watering, this is because the turf is in recovery after being kept in a roll and needs moisture as quickly as possible. Turf should then be watered in the shade or when the sun is low; this will prevent possible scorching of the leaves. If the turf is wedged in closely and if insufficient water is being applied, they will start to shrink as the grass is using the water held in the roll very quickly - this is an indication that it needs watering straight away. If rain is forecast, turf should still be watered in; it may only be a small shower or it may not rain at all. If it does rain it will be a bonus.
Expect to water turf twice a day in the turf's first week. The turf must not dry out, but do not water to the point that the soil becomes saturated; over-watering can be a problem especially on heavier soils. As your turf establishes, roots are sent into the soil at the rate of 12.5mm a week. A mature turf on most UK soils will have roots between 150-250mm deep. Until the roots gets beyond the first 25mm of topsoil, the sun and wind can play a big roll in drying out the soil as well as the turf absorbing moisture.
As you water, it will percolate down into the soil, eventually draining beyond the roots. It must also be remembered that other roots such as tree roots will also be taking in water - an area of tree shade may need to be watered just as much as full sunshine.
The amount of water to be applied ultimately depends on location, shade, sun and type of soil, but you should not let turf sit in water as this will lead to root rot. If the preparation has been done correctly the water should drain away from the root zone reasonably quickly leaving the soil moist.
Water can be applied with a garden sprinkler by manual operation or with a timer. If the area is large it is worth considering an irrigation system as this could be installed prior to laying the turf. The duration of the watering should be between 20-30 minutes. During winter months it would not be necessary to water the turf.
After a year of establishment your new lawn will be well-rooted and watering can be limited to times of drought.